Doctoral Dissertation Research: Temporal and Spatial Patterns of Holocene Peatland Carbon Dynamics, West Siberian Lowland, Russia

泥炭地生态系统是全球碳循环的重要组成部分，因为在全新世（过去11000年）的过程中，它们作为有机土壤从大气中吸收了最大的单一陆地碳储量。泥炭地生态系统也是当代大气甲烷最重要的来源之一。在一系列高纬度地区使用各种方法进行的研究表明，北部泥炭地对气候变化高度敏感，以至于它们可以在每隔一年从大气净碳汇转变为净碳源。然而，这些巨大的碳储量未来将在日益受到人为温室气体干扰的气候中扮演何种角色仍不确定。这些系统的长期碳交换行为需要多年的观测，并且对十年或更长时间内泥炭地碳循环对气候的响应的基本认识仍然很差。本博士论文研究项目将运用古生态学工具研究西伯利亚泥炭地生态系统对过去气候变化的响应。西西伯利亚低地含有世界上密度最高的泥炭碳，但相对于芬诺斯坎德、欧洲和北美的泥炭矿床，研究很少。本研究将利用可识别的植物遗骸、土壤碳特征和来自大量岩心的泥炭14-C AMS年龄测定的信息来研究西伯利亚西部泥炭地碳动态的时空格局。具体而言，该项目将(1)确定全新世泥炭-大气甲烷交换中重要的泥炭历史主要生态变化的时空性质，(2)确定这些变化如何影响全新世泥炭积累速率，以及(3)评估WSL中碳积累的近期模式，以提高对现代变暖敏感性的理解。北半球陆地生态系统已被确定为过量人为二氧化碳的全球关键碳汇，然而，这一重要碳汇的年强度是可变的。陆地上最大的碳封存集中在北美和欧亚大陆内部的泥炭中。西西伯利亚低地的研究对于评估北部高纬度环境在全球碳循环中的作用至关重要，因为该地区历史上的碳积累研究相对缺乏，这里存在大量的碳储量，而且它位于最近北极每十年变暖1摄氏度到2摄氏度的焦点。此前由美国国家科学基金会资助的俄美合作研究已经产生了迄今为止最高质量的泥炭碳清单，以及从遥远的西西伯利亚低地收集的前所未有的难以获得的泥炭记录。这些初步研究已经确定了记录覆盖率的巨大空间差距，这与该地区南部泥炭碳的最大纬度储存相一致。这个博士论文研究改进奖将允许最后的实地活动到西伯利亚，并完成实验室分析。只有当这一空白被填补时，西西伯利亚低地碳积累历史的完整图景才能最终发展起来。该奖项还将提供支持，使有前途的学生建立一个强大的独立研究事业。

Peatland ecosystems are significant components in the global carbon cycle, as they have sequestered from the atmosphere the largest single terrestrial carbon stock as organic soils over the course of the Holocene (the last 11,000 years). Peatland ecosystems also are one of the most important contemporary sources of atmospheric methane. Research from a range of high-latitude locations using a variety of methods has revealed that northern peatlands are highly sensitive to climatic variation, to the extent that they can switch interannually from net atmospheric carbon sinks to net carbon sources. The future role that these massive carbon stocks will play in a climate increasingly perturbed by anthropogenic greenhouse gases remains uncertain, however. Long-term carbon exchange behavior of these systems requires many years of observation, and basic understanding of peatland carbon cycling response to climate over decadal or longer periods remains poor. This doctoral dissertation research project will apply paleoecological tools to investigate Siberian peatland ecosystem response to past climatic changes. The West Siberian Lowland contains the world's highest density of peat carbon, yet is poorly studied relative to Fennoscandian, European, and North American peat deposits. This research will use information in identifiable plant remains, soil carbon characteristics, and 14-C AMS age determinations of peat from a wide collection of cores to investigate spatiotemporal patterns of carbon dynamics in West Siberian peatlands. Specifically, the project will (1) determine the spatiotemporal nature of major ecological changes in peatland history important to Holocene peatland-atmosphere methane exchange, (2) determine how Holocene peat accumulation rates have been affected by these changes, and (3) assess recent patterns of C accumulation in the WSL towards increased understanding of their sensitivity to modern warming.Terrestrial Northern Hemisphere ecosystems have been identified as globally critical carbon sinks for excess anthropogenic carbon dioxide, however, the year-to-year strength of this important sink is variable. The greatest terrestrial concentration of sequestered carbon is stored in peats within the continental interiors of North America and Eurasia. Study of the West Siberian Lowland is crucial to the assessment of the role of northern high-latitude environments in the global carbon cycle owing to the relative paucity of historical carbon accumulation studies in the region, the massive carbon stocks present here, and its location at the focus of recent 1-degree Celsius to 2-degrees Celsius per decade Arctic warming. Previous NSF-funded Russian-American collaborative research has resulted in the highest quality peat carbon inventory to date as well as an unprecedented collection of hard-to-get peat records from the remote West Siberian Lowland. These initial studies have identified a large spatial gap in record coverage that is coincident with the maximum latitudinal storage of peat carbon in the south of the region. This Doctoral Dissertation Research Improvement award will allow a final field campaign to Siberia, and completion of laboratory analyses. A complete picture of West Siberian Lowland carbon accumulation history can only be conclusively developed when this gap is filled. This award also will provide support to enable a promising student to establish a strong independent research career.